Yarn feeding device

Abstract

A yarn feeding device comprises a stationary storage drum from which the yarn can be withdrawn. The yarn feeding device can be operated at a positive feeding mode and at a non-positive feeding mode by means of a rotatable yarn guiding member arranged at the withdrawal end. The yarn guiding member comprises at least one yarn engagement element adapted for engaging the yarn when the rotational speed of the yarn spiralling around the withdrawal end of the storage drum tends to exceed the rotational speed of the yarn guiding member. The yarn engagement element comes out of engagement with the yarn when the rotational speed of the guiding member exceeds the rotational speed of the yarn spiralling around the withdrawal end of the storage drum.

I claim: 
     
       1. A yarn feeding device for selective positive or non-positive feeding of yarn to a yarn consuming textile machine, said device comprising: a non-rotatable storage drum having a central axis, a peripheral storage surface and a withdrawal end;   a yarn winding-on member rotatably associated with said storage drum in order to form a yarn storage containing a plurality of yarn windings on said storage surface of said storage drum, said yarn being withdrawn from said storage surface over said withdrawal end at a withdrawal point which rotates around said axis with a rotational speed dependent on the yarn consumption of the textile machine;   a yarn guiding member arranged adjacent to said withdrawal end, said yarn guiding member being supported for rotation around said axis and being provided with a substantially circular guiding surface for guiding the withdrawn yarn adjacent the withdrawal point;   at least one yarn engaging element provided on said yarn guiding member and projecting over the guiding surface at least during periods of positive yarn feeding, said yarn engaging element having a front face and a rear catching-face as seen in the direction of rotation of the withdrawal point for hindering said yarn to pass the yarn engagement element during rotation of the withdrawal point; and   driving means connected with the winding-on member to rotatively drive the winding-on member relative to the drum;   the improvement comprising:   a variable-speed drive means separate from the driving means of the winding-on member and connected with said yarn guiding member to at least define the rotational speed of the yarn withdrawal point during positive feeding and for changing the rotational speed of the yarn withdrawal point during positive feeding; and   said yarn engagement element being arranged in fixed relationship on said yarn guiding member in order to project over said guiding surface during both positive and non-positive feeding.   
     
     
       2. A yarn feeding device according to claim 1, wherein said variable-speed drive means increases the rotational speed of the yarn guiding member over the rotational speed of the yarn withdrawal point under positive feeding in order to move the yarn out of engagement with said rear catching-face and to terminate positive feeding. 
     
     
       3. A yarn feeding device according to claim 2, wherein said front face of said yarn engaging element has an inclination with respect to the radial direction from said axis which is opposite to the direction of rotation of the yarn withdrawal point in order to allow the yarn to slide over the yarn engagement element as soon as the rotational speed of the yarn guiding member exceeds the rotational speed of the yarn withdrawal point after termination of positive feeding. 
     
     
       4. A yarn feeding device according to claim 1, wherein the front face of said yarn engaging element has an inclination with respect to the radial direction from said axis which is opposite to the direction of rotation of the yarn withdrawal point in order to allow the yarn to slide over said yarn engaging element as soon as the rotational speed of the yarn withdrawal point falls below the rotation speed of the yarn guiding member for starting non-positive feeding of yarn. 
     
     
       5. A yarn feeding device according to claim 1, wherein said yarn guiding member is formed as a ring having a radially inner surface which defines said circular guiding surface and having at least one projection which projects radially inwardly from said guiding surface, said projection defining thereon said front face, said front face as it projects radially inwardly also being sloped or inclined opposite to the direction of rotation of the yarn withdrawal point. 
     
     
       6. A yarn feeding device according to claim 5, wherein said yarn guiding member has a plurality of said projections formed thereon and projecting radially inwardly from said guiding surface in substantially uniformly angularly spaced relationship therearound. 
     
     
       7. A yarn feeding device according to claim 1, wherein said yarn guiding member has a radially outer surface defining said circular guiding surface and having at least one radially-outwardly extending projection defining said yarn engaging element, said projection defining said front face thereon with said front face being sloped or inclined opposite to the direction of rotation of the yarn withdrawal point as the projection projects radially outwardly. 
     
     
       8. A yarn feeding device according to claim 2, wherein said drive means rotatably drives said yarn guiding member during positive feeding at a first rotational speed in synchronism with the operational speed of the textile machine, and wherein said drive means rotatably drives said yarn guiding member during non-positive feeding at a second rotational speed exceeding said first rotational speed. 
     
     
       9. A yarn feeding device for selective positive or non-positive feeding of yarn to a yarn consuming textile machine, said device comprising: a non-rotatable storage drum having a central axis, a peripheral storage surface and a withdrawal end;   a yarn winding-on member rotatably associated with said storage drum in order to form a yarn storage containing a plurality of yarn windings on said storage surface of said storage drum, said yarn being withdrawn from said storage surface over said withdrawal end at a withdrawal point which rotates around said axis with a rotational speed dependent on the yarn consumption of the textile machine;   a yarn guiding member arranged adjacent to said withdrawal end, said yarn guiding member being supported for rotation around said axis and being provided with a substantially circular guiding surface for guiding the withdrawn yarn adjacent the withdrawal point;   at least one yarn engaging element provided on said yarn guiding member and projecting over the guiding surface at least during periods of positive yarn feeding, said yarn engaging element having a front face and a rear catching-face as seen in the direction of rotation of the withdrawal point for hindering said yarn to pass the yarn engagement element during rotation of the withdrawal point; and   drive means connected with the winding-on member and the yarn guiding member respectively, in order to at least define the rotational speed of the yarn withdrawal point during positive feeding;   the improvement comprising:   said front face of said yarn engaging element having an inclination with respect to the radial direction to said axis opposite to the direction of rotation of the yarn withdrawal point in order to allow the yarn to slide over said yarn engaging element as soon as the rotational speed of the yarn withdrawal point falls below the rotational speed of the yarn guiding member for starting non-positive yarn feed.   
     
     
       10. A yarn feeding device according to claim 9, wherein said yarn engaging element is arranged in fixed relationship on said yarn guiding member in order to project over said guiding surface during both positive and non-positive feeding. 
     
     
       11. A yarn feeding device according to claim 10, wherein said yarn guiding member is continuously driven during both positive and non-positive feeding at a rotational speed in synchronism with the operational speed of the textile machine. 
     
     
       12. A yarn feeding device according to claim 9, wherein the drive means includes a variable speed drive connected to the yarn guiding member for driving the yarn guiding member separate from the winding-on member. 
     
     
       13. A yarn feeding device for selective positive or non-positive feeding of yarns to a yarn consuming textile machine, said device comprising: a non-rotatable yarn storage drum having a central longitudinally-extending axis, a surrounding peripheral storage surface, and a withdrawal end;   a yarn winding-on member disposed adjacent said storage drum and supported for rotation about said central axis for winding yarn onto said peripheral storage surface to form a yarn storage thereon containing a plurality of yarn windings, said yarn being withdrawal from said storage surface over said withdrawal end at a withdrawal point which orbits around said axis at a rotational speed dependent on the yarn consumption of the textile machine;   a yarn guiding member arranged adjacent to the withdrawal end of said storage drum and being supported for rotation about said axis, said yarn guiding member defining thereon a substantially circular guiding surface which surrounds said axis and guides the withdrawn yarn adjacent the withdrawal point;   at least one yarn engaging element fixedly provided on said yarn guiding member and projecting radially outwardly from the guiding surface so as to be disposed in the path of the withdrawal yarn as the withdrawal point rotates during both positive and non-positive feeding, said yarn engaging element having a front face and a rear yarn-catching face as seen in the direction of rotation of the withdrawal point, said front face permitting the withdrawal yarn to pass in one direction over the yarn engaging element while the rear yarn-catching face restricts the yarn from passing over the yarn engaging element in the opposite direction; and   variable-speed drive means for rotatably driving the yarn guiding member separate from the winding-on member to at least define the rotational speed of the yarn withdrawal point during positive feeding and for also permitting non-positive feeding of yarn without requiring any rethreading of the yarn, said drive means causing the yarn guiding member to be driven at a rotational speed which exceeds the rotation of the withdrawal point during non-positive feeding.